Question: Solve for $x$ and $y$ using substitution. ${-2x+6y = 8}$ ${y = 3x-12}$
Since $y$ has already been solved for, substitute $3x-12$ for $y$ in the first equation. ${-2x + 6}{(3x-12)}{= 8}$ Simplify and solve for $x$ $-2x+18x - 72 = 8$ $16x-72 = 8$ $16x-72{+72} = 8{+72}$ $16x = 80$ $\dfrac{16x}{{16}} = \dfrac{80}{{16}}$ ${x = 5}$ Now that you know ${x = 5}$ , plug it back into $\thinspace {y = 3x-12}\thinspace$ to find $y$ ${y = 3}{(5)}{ - 12}$ $y = 15 - 12$ $y = 3$ You can also plug ${x = 5}$ into $\thinspace {-2x+6y = 8}\thinspace$ and get the same answer for $y$ : ${-2}{(5)}{ + 6y = 8}$ ${y = 3}$